|
 Friday, October 21, 2011 |
| Lighting a Bulb from Ground. |
|
Years ago we did a little experiment to demonstrate a common networking problem. We were networking some little user terminals that were used in factories to keep track of production. These were of our own design. In this design we were networking the various terminals together using low voltage wire and a serial protocol. We were using RS-422 which uses a balanced differential pair of signals. As a demonstration of the voltage potentials that can exist we got a drop light and connected each of its' wire's to some equipment on each end of the factory floor.  We connected to neutral on each end. We then tried the chassis grounds as well.
Don't you know we were able to get that light bulb to light! We never did track down the source of the actual problem. It could be the equipment was badly grounded. Or that the equipment was not grounded at all. In any case we wanted OUR boxes to work in as many different situations as possible and be as reliable as possible.
This is were we came up with a common mode voltage requirement for our serial network differential signaling. A requirement is born. |
damon at 4:44 PM |
(1) Comments |
Add a comment |
Permalink
|
|
|
|